Our invention relates to the field of recumbent bicycles.
An ever-increasing segment of the cycling public, particularly in the United States, rides and enjoys recumbent bicycles due to their comfort and performance. The basic configuration for a recumbent bicycle places the pedals ahead of, rather than below, the cyclist. This configuration allows the use of a more comfortable seat with seat back, which is typically placed lower to the ground than on ordinary bicycles. However, it also leads to problems that are distinctive to the field of recumbent bicycles.
One of the most important of these problems is shock absorption. As the recumbent cyclist is in a seated position with legs forward, he (or she) cannot absorb the extreme jolts and shocks associated with riding over rough surfaces or traversing potholes by utilizing his legs as shock absorbers. The bicycle and its frame must handle all shock absorption. This has led many manufacturers to utilize a bifurcated frame with a pivot placed in a structural member between the front wheel and the rear wheel. This pivot serves (in combination with a shock absorber of some type) to help absorb the shocks of the ride.
Unfortunately, the presence of a bifurcated frame has led to a problem for which no adequate solution has been found. This problem is formally referred to in the art as xe2x80x9cpedaling induced suspension activationxe2x80x9d, and more informally referred to as xe2x80x9cpogoingxe2x80x9d. It occurs when the cyclist pushes a pedal forward, putting stress on the upper part of the chain linkage between the pedal sprocket (which is ahead of the rider) or an intermediate mid-drive sprocket and the rear wheel sprocket. In effect, it causes this section of chain to temporarily shorten, which, in turn, causes the pivot to move upward and the bicycle frame to become temporarily shorter. As the pedals move into a more neutral position before the beginning of the next drive stroke by the rider""s other foot, the pivot sags downward and the frame lengthens. This situation can rapidly develop into a steady, undesirable, up-and-down oscillation of the rider and framexe2x80x94xe2x80x9cpogoingxe2x80x9d.
Another important problem involves provision of adequate means for seat positioning. Positioning of the seat vis-à-vis the pedals becomes a more critical issue on a recumbent bicycle. The recumbent cyclist does not have the option of standing to pedal and thereby minimizing the importance of seat positioning. Further, he cannot adjust his distance to the pedals by sliding slightly forward or backward on the seat, as is possible for the user of a standard bicycle. Finally, the leverage relied upon by the recumbent cyclist is gained by working against the seat back of the recumbent bicycle seat. It is, therefore, absolutely necessary that the recumbent bicycle seat be not only comfortable, but also precisely and minutely adjustable for the comfort and mechanical advantage of the user. At the same time, the seat must be able to maintain its position, once established, against the constant and repeated force exerted by the rider as he pushes back against the seat on each pedal stroke.
No adequate solution to this problem has been achieved to date in the art of recumbent bicycles. Some manufacturers utilize seats with anchoring members that fit into rigid track notches. Such seats do not slide, but they lack the minute adjustability sought by discerning riders. Other manufacturers have utilized seats that are freely adjustable by sliding on a seat track. The distance between such seats and the pedals of the recumbent bicycle can be adjusted with precision. However, such seats are generally maintained in position by a clamp attached to the track. This clamp is, in turn, tightened and held in position by tightening a screw threaded bolt or other member. Screw threaded elements of this type are difficult to tighten to the degree necessary to hold the bicycle seat in position. Most have shown an inevitable tendency to begin moving over a period of time under the stresses created by pedaling the recumbent bicycle. In addition, such clamps are not easily and freely adjustable, but require the use of tools to loosen, adjust, and re-tighten.
Our invention solves the problems outlined above; significantly improves recumbent bicycle performance, comfort, and ease of use; and involves or creates numerous other subsidiary improvements and inventions of significance in the field of recumbent bicycles. It is hinged on our finding that the problems described above are interrelated and can both be solved simultaneously by (i) the use of a cantilevered bicycle seat in conjunction with (ii) a coaxial bicycle pivot and mid-drive sprocket. The first solution also led to the creation of a bicycle seat that was stable, was easily adjustable without tools, and could be adjusted with the type of precision demanded by the field. The second solution, in turn, led to the creation of a recumbent bicycle that was foldable. This innovation is extremely desirable for the recumbent cyclist as it leads to a bicycle that can be folded to occupy a smaller space. This not only eases storage problems; it creates a recumbent bicycle that can be placed easily in an automobile trunk or other vehicle storage area for transport to settings where the user wishes to ride his bicycle. Thus, it also greatly increases bicycle portability. These and other innovations unique to our design will become apparent upon review of the accompanying drawings and the more detailed description that follows.